A solenoid device having an electromagnetic coil which generates magnetic flux when current is passed, a plurality of plungers, and a fixed core made of soft magnetic material is known (refer to Japanese Unexamined Patent Application Publication No. 2005-222871).
The solenoid device is constructed to generate magnetic force by passing current to the electromagnetic coil so that the plungers are attracted by the fixed core. A spring member is disposed between the plungers and the fixed core. When passage of current to the electromagnetic coil is stopped, the magnetic force decreases, and the plungers are apart from the fixed core by the elastic force of the spring member. In such a manner, the plungers are moved forward/backward. By the forward/backward operation of the plungers, for example, the solenoid device is used for turning on/off a switch or opening/closing a valve.
There is a solenoid device in which a plurality of plungers is attracted in predetermined order. Such a solenoid device is used for, for example, a circuit which turns on a plurality of switches in predetermined order. The solenoid device is provided with a plurality of electromagnetic coils, and a plunger is disposed in the center of each of the electromagnetic coils. By passing current to each of the electromagnetic coils, the plurality of plungers is attracted separately. The order of attracting the plungers is controlled by a control circuit connected to the electromagnetic coils.
In the conventional solenoid device, however, the electromagnetic coils of the same number as that of the plungers are necessary to attract the plurality of plungers in order, so that the number of the electromagnetic coils increases. It causes a problem that the manufacture cost of the solenoid device tends to be high. Consequently, a solenoid device in which a plurality of plungers can be attracted in predetermined order and whose manufacture cost is low is demanded.